1. Field of the Invention
The present invention relates to an instant photo film pack. More particularly, the present invention relates to an instant photo film pack in which an outlet slit can be shielded reliably from ambient light.
2. Description Related to the Prior Art
An instant photo film pack for use with an instant camera is known in the field of photosensitive material. JP-A 7-209814 discloses an example of the photo film pack, which is constituted by a pack case of hard plastic shaped as a box, and contains self-processing photo film units of a mono-sheet type. Each of the photo film units includes an exposure portion of a photosensitive sheet, a solution pod and a trap portion. The exposure portion includes a photosensitive layer and a light receiving layer. The solution pod encloses processing solution. The trap portion traps and hardens the surplus part of the processing solution.
There are an exposure opening and an outlet slit in the case of the photo film pack. The outlet slit is formed for exiting of each exposed one of the photo film units. A light-shielding cover sheet of hard plastics is laid on an exposure surface of a first one of the photo film units, and closes the exposure opening to avoid entry of light.
The photo film pack is inserted into a photo film loading chamber of the instant camera. A shutter release button of the instant camera is depressed to take an exposure. In response to this, a claw mechanism, incorporated in the body of the instant camera as well-known in the art, pushes only the exposed one of the photo film units and ejects it through the outlet slit of the photo film pack. The photo film unit is nipped by a set of spreader rollers, and advanced toward a camera outlet of the instant camera. The spreader roller set spreads processing solution on an exposure surface of the photo film unit to develop the photo film unit. At the same time, a succeeding one of the photo film units is shifted forwards and becomes set on the exposure opening.
There is a light-shielding flap or thin sheet of resin attached to the outlet slit of the photo film pack for avoiding entry of ambient light into the photo film pack and fogging of an unexposed one of the photo film units. For attaching the light-shielding flap, adhesive agent is used, an example of which is a hot-melt type for the reason of productivity of the photo film pack.
The light-shielding flap of the prior art is attached by use of a simply straight region of adhesion to the outlet slit of the photo film pack. As the temperature changes from high temperature of hot-melt adhesion to low temperature, wrinkles or shrinkage in the light-shielding flap is likely to occur at the outlet slit. A space or gap may be created with the outlet slit typically at an end of the light-shielding flap. Ambient light may enter through the space of the gap to fog or expose the photo film units.